I have a JD 2940 with an Allied 595 loader. The other day I noticed it was down a bit of hydralic fluid. I added nearly a gallon and it was at the full mark. Today I started the tractor to use the loader. The loader raised about 8 inches and then stopped dead. When I lower it it goes down very slowly. I shut the tractor off and looked for binding or something blocking it. It was free. Every time I tried to raise the loader arms it comes up about 8 to 12 inches and then stops. The bucket worked normally so I switched the lines from the bucket to the arms. They raised and lowered normally. Is there a bleed fitting on the control unit? Could it have an air or water lock preventing it from operating? Do I need to replace or rebuild the hydralic control unit? Any help would be appreciated.